Importance of β2AR elevation for re-endothelialization capacity mediated by late endothelial progenitor cells in hypertensive patients

Dysfunction of late endothelial progenitor cells (EPCs) has been suggested to be associated with hypertension. β2-Adrenergic receptor (β2AR) is a novel and key target for EPC homing. Here, we proposed that attenuated β2AR signaling contributes to EPCs dysfunction, whereas enhanced β2AR signaling restores EPCs' functions in hypertension. EPCs derived from hypertensive patients exhibited reduced cell number, impaired in vitro migratory and adhesion abilities, and impaired re-endothelialization after transplantation in nude mice with carotid artery injury. β2AR expression of EPCs from hypertensive patients was markedly downregulated, whereas the phosphorylation of the p38 mitogen-activated protein kinase (p38-MAPK) was elevated. The cleaved caspase-3 levels were elevated in EPCs. The overexpression of β2AR in EPCs from hypertensive patients inhibited p38-MAPK signaling, whereas it enhanced in vitro EPC proliferation, migration, and adhesion and in vivo re-endothelialization. The β2AR-mediated effects were attenuated by treating the EPCs with a neutralizing monoclonal antibody against β2AR, which could be partially antagonized by the p38-MAPK inhibitor SB203580. Moreover, shear stress stimulation, a classic nonpharmacological intervention, increased the phosphorylation levels of β2AR and enhanced the in vitro and in vivo functions of EPCs from hypertensive patients. Collectively, the current investigation demonstrated that impaired β2AR/p38-MAPK/caspase-3 signaling at least partially reduced the re-endothelialization capacity of EPCs from hypertensive patients. Restoration of β2AR expression and shear stress treatment could improve their endothelial repair capacity by regulating the p38-MAPK/caspase-3 signaling pathway. The clinical significance of β2AR in endothelium repair still requires further investigation.NEW & NOTEWORTHY Impaired β2-adrenergic receptor (β2AR) expression with an elevation of p38-MAPK/caspase-3 signaling at least partially contributes to the decline of re-endothelialization capacity of late endothelial progenitor cells (EPCs) from hypertensive patients. β2AR gene transfer and shear stress treatment improve the late EPC-mediated enhancement of the re-endothelialization capacity in hypertensive patients through activating β2AR/p38-MAPK/caspase-3 signaling. The present study is the first to reveal the potential molecular mechanism of the impaired endothelium-reparative capacity of late EPCs in hypertension after vascular injury and strongly suggests that β2AR is a novel and crucial therapeutic target for increasing EPC-mediated re-endothelialization capacity in hypertension.

Platelets of Healthy Origins Promote Functional Improvement of Atherosclerotic Endothelial Progenitor Cells

The purpose was to evaluate the effect of platelets on functional properties of late endothelial progenitor cells (EPCs), in the direct co-culture conditions, and to investigate the involved mediators, in experimental induced atherosclerosis. The late EPCs obtained from two animal groups, hypertensive-hyperlipidemic (HH) and control (C) hamsters, named late EPCs-HH and late EPCs-C, were co-incubated with or without platelets isolated from both groups. Our results have showed that exposure to platelets from control animals: (i) promoted the late EPCs-C capacity to form colonies and capillary-like structures, and also to proliferate and migrate; (ii) improved the functional properties of late EPCs-HH; (iii) strengthened the direct binding EPCs-platelets; (iv) increased SDF-1α,VEGF, PDGF, and reduced CD40L, IL-1β,-6,-8 levels; and (v) enhanced miR-223 and IGF-1R expressions. Platelets from HH group diminished functional abilities for both EPC types and had opposite effects on these pro-angiogenic and pro-inflammatory molecules. Furthermore, testing the direct effect of miR-223 and IGF-1R on late EPCs disclosed that these molecular factors improve late EPC functional properties in atherosclerosis in terms of stimulation of the proliferation and migration abilities. In conclusion, in vitro exposure to platelets of healthy origins had a positive effect on functional properties of atherosclerotic late EPCs. The most likely candidates mediating EPC-platelet interaction can be SDF-1α, VEGF, CD40L, PDGF, IL-1β,-6,-8, miR-223, and IGF-1R. The current study brings evidences that the presence of healthy origin platelets is of utmost importance on functional improvement of EPCs in atherosclerosis.

IFN-γ enhances the wound healing effect of late EPCs (LEPCs) via BST2-mediated adhesion to endothelial cells

Circulating late endothelial progenitor cells (LEPCs) home to injured vessels, initiating blood vessel regeneration. This process requires the initial adhesion of LEPCs to endothelial cells within the wounded site. In this study, treating LEPCs with IFN-γ enhanced wound healing through BST2-mediated adhesion to endothelial cells. We found that IFN-γ significantly upregulated BST2 expression in both LEPCs and ECs and increased tube formation in LEPCs. Upregulated BST2 increased LEPC adhesion to ECs through a tight homophilic interaction of its extracellular domain. Finally, when the IFN-γ-treated LEPCs were injected into the wounded mouse tail vein, superior therapeutic effects of wound closure were observed. This study provides a useful application to enhance the adhesion of LEPCs for vessel regeneration and wound closure.